diff --git a/src/Serilog.Enrichers.Thread/Enrichers/ThreadIdEnricher.cs b/src/Serilog.Enrichers.Thread/Enrichers/ThreadIdEnricher.cs
index a19dc94..2ad07e5 100644
--- a/src/Serilog.Enrichers.Thread/Enrichers/ThreadIdEnricher.cs
+++ b/src/Serilog.Enrichers.Thread/Enrichers/ThreadIdEnricher.cs
@@ -31,7 +31,7 @@ public class ThreadIdEnricher : ILogEventEnricher
         /// <summary>
         /// The cached last created "ThreadId" property with some thread id. It is likely to be reused frequently so avoiding heap allocations.
         /// </summary>
-        private LogEventProperty _lastValue;
+        private LogEventProperty? _lastValue;
 
         /// <summary>
         /// Enrich the log event.
diff --git a/src/Serilog.Enrichers.Thread/Enrichers/ThreadNameEnricher.cs b/src/Serilog.Enrichers.Thread/Enrichers/ThreadNameEnricher.cs
index cffa6c0..d9b8cf4 100644
--- a/src/Serilog.Enrichers.Thread/Enrichers/ThreadNameEnricher.cs
+++ b/src/Serilog.Enrichers.Thread/Enrichers/ThreadNameEnricher.cs
@@ -32,7 +32,7 @@ public class ThreadNameEnricher : ILogEventEnricher
         /// <summary>
         /// The cached last created "ThreadName" property with some thread name. It is likely to be reused frequently so avoiding heap allocations.
         /// </summary>
-        private LogEventProperty _lastValue;
+        private LogEventProperty? _lastValue;
 
         /// <summary>
         /// Enrich the log event.
diff --git a/src/Serilog.Enrichers.Thread/Serilog.Enrichers.Thread.csproj b/src/Serilog.Enrichers.Thread/Serilog.Enrichers.Thread.csproj
index a9bd8d6..aa25c84 100644
--- a/src/Serilog.Enrichers.Thread/Serilog.Enrichers.Thread.csproj
+++ b/src/Serilog.Enrichers.Thread/Serilog.Enrichers.Thread.csproj
@@ -17,6 +17,8 @@
     <PackageProjectUrl>http://serilog.net</PackageProjectUrl>
     <PackageLicenseExpression>Apache-2.0</PackageLicenseExpression>
     <GenerateAssemblyVersionAttribute>false</GenerateAssemblyVersionAttribute>
+    <LangVersion>latest</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>